E9 on a Mitsubishi Electric heat pump: Outdoor unit receives no signal from indoor unit (FTC)
Short answer
On a Mitsubishi Electric heat pump, E9 means: Outdoor unit receives no signal from indoor unit (FTC). The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 9 sources
What it means
On the Ecodan
The manual says: Outdoor unit receives no signal from indoor unit (FTC).
Part involved: FTC-outdoor connecting wire.
When it shows: Outdoor unit receives no signal from indoor unit (FTC).
Likely causes:
- Outdoor or indoor unit switched off; connecting cable damaged or loose (see outdoor unit E9 record for outdoor-side detail).
On the Ecodan Puhz Sw Split
The manual says: Indoor/outdoor unit communication error - transmitting error detected by outdoor unit.
Part involved: Indoor/outdoor connecting wire; outdoor controller board.
When it shows: '0' received 30 times continuously though outdoor board transmitted '1', or no blank transmission path found for 3 minutes.
Likely causes:
- 1 Indoor/outdoor unit connecting wire has contact failure; 2 Defective communication circuit of outdoor controller circuit board; 3 Noise has entered power supply; 4 Noise has entered indoor/outdoor connecting wire.
On the Ecodan Puhz W Monobloc
The manual says: Indoor/outdoor unit communication error - transmitting error detected by outdoor unit.
Part involved: Indoor/outdoor connecting wire; outdoor controller board.
When it shows: '0' received 30 times continuously though outdoor board transmitted '1', or no blank transmission path found for 3 minutes.
Likely causes:
- 1 Indoor/outdoor unit connecting wire has contact failure; 2 Defective communication circuit of outdoor controller circuit board; 3 Noise has entered power supply; 4 Noise has entered indoor/outdoor connecting wire.
On the Ecodan R290 Puz Wz
The manual says: Indoor/outdoor unit communication error - transmitting error detected by outdoor unit.
Part involved: Indoor/outdoor connecting wire; outdoor controller board.
When it shows: '0' received 30 times continuously though outdoor board transmitted '1', or no blank transmission path found for 3 minutes.
Likely causes:
- 1 Indoor/outdoor unit connecting wire has contact failure; 2 Defective communication circuit of outdoor controller circuit board; 3 Noise has entered power supply; 4 Noise has entered indoor/outdoor connecting wire.
On the Ecodan R32 Puz Wm
The manual says: Indoor/outdoor unit communication error - transmitting error detected by outdoor unit.
Part involved: Indoor/outdoor connecting wire; outdoor controller board.
When it shows: '0' received 30 times continuously though outdoor board transmitted '1', or no blank transmission path found for 3 minutes.
Likely causes:
- 1 Indoor/outdoor unit connecting wire has contact failure; 2 Defective communication circuit of outdoor controller circuit board; 3 Noise has entered power supply; 4 Noise has entered indoor/outdoor connecting wire.
On the Ecodan R32 Zubadan Puz Hwm
The manual says: Indoor/outdoor unit communication error - transmitting error detected by outdoor unit.
Part involved: Indoor/outdoor connecting wire; outdoor controller board.
When it shows: '0' received 30 times continuously though outdoor board transmitted '1', or no blank transmission path found for 3 minutes.
Likely causes:
- 1 Indoor/outdoor unit connecting wire has contact failure; 2 Defective communication circuit of outdoor controller circuit board; 3 Noise has entered power supply; 4 Noise has entered indoor/outdoor connecting wire.
On the Ecodan Ultra Quiet Puhz W Vaa
The manual says: Indoor/outdoor unit communication error - transmitting error detected by outdoor unit.
Part involved: Indoor/outdoor connecting wire; outdoor controller board.
When it shows: '0' received 30 times continuously though outdoor board transmitted '1', or no blank transmission path found for 3 minutes.
Likely causes:
- 1 Indoor/outdoor unit connecting wire has contact failure; 2 Defective communication circuit of outdoor controller circuit board; 3 Noise has entered power supply; 4 Noise has entered indoor/outdoor connecting wire.
On the Ecodan Zubadan Puhz Hw Monobloc
The manual says: Indoor/outdoor unit communication error - transmitting error detected by outdoor unit.
Part involved: Indoor/outdoor connecting wire; outdoor controller board.
When it shows: '0' received 30 times continuously though outdoor board transmitted '1', or no blank transmission path found for 3 minutes.
Likely causes:
- 1 Indoor/outdoor unit connecting wire has contact failure; 2 Defective communication circuit of outdoor controller circuit board; 3 Noise has entered power supply; 4 Noise has entered indoor/outdoor connecting wire.
On the Ecodan Zubadan Puhz Shw Split
The manual says: Indoor/outdoor unit communication error - transmitting error detected by outdoor unit.
Part involved: Indoor/outdoor connecting wire; outdoor controller board.
When it shows: '0' received 30 times continuously though outdoor board transmitted '1', or no blank transmission path found for 3 minutes.
Likely causes:
- 1 Indoor/outdoor unit connecting wire has contact failure; 2 Defective communication circuit of outdoor controller circuit board; 3 Noise has entered power supply; 4 Noise has entered indoor/outdoor connecting wire.
Is it safe?
On the Ecodan
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-resetting; code remains until reset.
Manual reset: Installation manuals: press F4 (RESET) then F3 (Yes) on the main remote controller (older controllers: hold button E for 3 s); 'To cancel error codes please switch system off'. Fix the cause first.
On the Ecodan Puhz Sw Split
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-recovering in the service manual; code is logged in the outdoor unit error history.
Manual reset: Clear via RESET on the main remote controller after the cause is fixed; service manual actions include switching power off and on to recheck.
On the Ecodan Puhz W Monobloc
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-recovering in the service manual; code is logged in the outdoor unit error history.
Manual reset: Clear via RESET on the main remote controller after the cause is fixed; service manual actions include switching power off and on to recheck.
On the Ecodan R290 Puz Wz
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-recovering in the service manual; code is logged in the outdoor unit error history.
Manual reset: Clear via RESET on the main remote controller after the cause is fixed; service manual actions include switching power off and on to recheck.
On the Ecodan R32 Puz Wm
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-recovering in the service manual; code is logged in the outdoor unit error history.
Manual reset: Clear via RESET on the main remote controller after the cause is fixed; service manual actions include switching power off and on to recheck.
On the Ecodan R32 Zubadan Puz Hwm
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-recovering in the service manual; code is logged in the outdoor unit error history.
Manual reset: Clear via RESET on the main remote controller after the cause is fixed; service manual actions include switching power off and on to recheck.
On the Ecodan Ultra Quiet Puhz W Vaa
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-recovering in the service manual; code is logged in the outdoor unit error history.
Manual reset: Clear via RESET on the main remote controller after the cause is fixed; service manual actions include switching power off and on to recheck.
On the Ecodan Zubadan Puhz Hw Monobloc
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-recovering in the service manual; code is logged in the outdoor unit error history.
Manual reset: Clear via RESET on the main remote controller after the cause is fixed; service manual actions include switching power off and on to recheck.
On the Ecodan Zubadan Puhz Shw Split
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-recovering in the service manual; code is logged in the outdoor unit error history.
Manual reset: Clear via RESET on the main remote controller after the cause is fixed; service manual actions include switching power off and on to recheck.
What you can check
- Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. A power cycle is a Mitsubishi first step for communication codes: switching the heat pump off and on at its isolator (outdoor and indoor supplies) once is acceptable.
What the engineer will check
On the Ecodan
- Check both units are switched on; check connecting cable for damage or loose connections; refer to outdoor unit service manual.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan Puhz Sw Split
- 1 Check disconnection or looseness of indoor/outdoor connecting wire; 2-4 Turn power off and on again; replace outdoor controller board if displayed again.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan Puhz W Monobloc
- 1 Check disconnection or looseness of indoor/outdoor connecting wire; 2-4 Turn power off and on again; replace outdoor controller board if displayed again.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan R290 Puz Wz
- 1 Check disconnection or looseness of indoor/outdoor connecting wire; 2-4 Turn power off and on again; replace outdoor controller board if displayed again.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan R32 Puz Wm
- 1 Check disconnection or looseness of indoor/outdoor connecting wire; 2-4 Turn power off and on again; replace outdoor controller board if displayed again.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan R32 Zubadan Puz Hwm
- 1 Check disconnection or looseness of indoor/outdoor connecting wire; 2-4 Turn power off and on again; replace outdoor controller board if displayed again.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan Ultra Quiet Puhz W Vaa
- 1 Check disconnection or looseness of indoor/outdoor connecting wire; 2-4 Turn power off and on again; replace outdoor controller board if displayed again.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan Zubadan Puhz Hw Monobloc
- 1 Check disconnection or looseness of indoor/outdoor connecting wire; 2-4 Turn power off and on again; replace outdoor controller board if displayed again.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan Zubadan Puhz Shw Split
- 1 Check disconnection or looseness of indoor/outdoor connecting wire; 2-4 Turn power off and on again; replace outdoor controller board if displayed again.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
What you might notice
What owners and engineers report
41 owner and engineer reports mention this.
- Controller / thermostat problem on the Ecodan: 14 reports
- No heating on the Ecodan: 9 reports
- No hot water on the Ecodan: 9 reports
- Controller display blank on the Ecodan: 5 reports
- Intermittent fault on the Ecodan: 2 reports
- Controller / thermostat problem on the Ecodan R32 Puz Wm: 1 report
- Intermittent fault on the Ecodan Ultra Quiet Puhz W Vaa: 1 report
Sources
- Ecodan FTC7 PAC-IF08(1-3)B-E Installation Manual (DG79H200H01) ↗ · DG79H200H01 · page 32 (PDF p.33, 6.2 Self-check) · Reviewed 23 September 2026
- Ecodan PUHZ-SW(75-100-120)(V-Y)HA-BS Service Manual (OCH755) ↗ · OCH755 · page OCH755 p.29; OCH525C p.27 · Reviewed 23 September 2026
- Ecodan PUHZ-W112VHA-BS Service Manual (OCH562D) ↗ · OCH562D · page OCH562D p.24; OCH605A p.21; OCH465D p.25; OCH439N p.60 · Reviewed 23 September 2026
- PUZ-WZ(85-100-120)(V-Y)AA(-BS) Service_Manual (OCH880) ↗ · OCH880 · page OCH880 p.44; OCH816 p.40 · Reviewed 23 September 2026
- Ecodan PUZ-WM(50-60-85-112)V(H-A)A Service Manual (OCH727A) ↗ · OCH727A · page 30 · Reviewed 23 September 2026
- Ecodan PUZ-HWM140(V-Y)HA Service Manual (OCH748A) ↗ · OCH748A · page 26 · Reviewed 23 September 2026
- PUHZ-W85-112VAA(-BS) Service Manual (OCH681) ↗ · OCH681 · page 21 · Reviewed 23 September 2026
- Ecodan PUHZ-HW140VHA2-BS / PUHZ-HW140YHA2-BS Service Manual (OCH439N) ↗ · OCH439N · page 60 · Reviewed 23 September 2026
- PUHZ-SHW112-140V/YHA Service Manual (OCH526) ↗ · OCH526 · page 31 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026